Wall mounted resistor



United States Patent O WALL MOUNTED RESISTOR George Risk, Columbus,Nehru, assignor to Dale Products, Inc, Columbus, Nebr.

Application March 21, 1955, Serial No. 495,726

6 Claims. (Cl. 201-63) This invention relates to resistors forelectronic circuits and more particularly it is an object of theinvention to provide a resistor adapted to be mounted through a wall ofthe chassis of such a circuit, the resistor being of miniature size forthe conservation of space.

It has heretofore been recognized as desirable to construct a resistorin a way adapted to be mounted through a hole in a wall of a chassis.However, it has been thought impossible to construct a resistor for suchmounting and which would further be of miniature form to conserve spacewithout sacrificing the power rating of the resistor. This has beenbecause resistors have been constructed heretofore with their heatingelements in the shape of small cylinders with terminal wires extendingoutwardly from each end.

In a wall-mounted resistor it is necessary for both terminals or leadsto extend outwardly from only one end of the resistor. Obviously thiswould necessitate causing one of the leads to be doubled back alon theoutside of the resistor. In such a construction the lead would have tobe insulated from the remainder of the resistor and would also have tobe spaced from it a considerable distance in order to prevent dielectricbreakdown of the insulation between the two leads.

An objective and concept of my invention is to make it possible for theresistor to be made of small size through attaching one of the leads tothe inner side of its cap, rather than the outer side as is customary,and extending this lead down through the center of the hollowcylindrical resistor coil supporting member.

A particular object is to provide a resistor as described the housing ofwhich is adapted to be drawn tightly against a wall of a chassis forcontact therewith over a substantial and large area for the use of thewall to dissipate heat from the resistor, further making practical theuse of a very miniature size of resistor without sacrificing the powerrating thereof.

Still another object is to provide an aperture in that end of thehousing which is opposite the leads for permitting the escape of fluidinsulating material therethrough during insertion of the resistor core,the fluid insulating material then filling the space between the coreand resistor housing as is common in the prior art.

Still further objects of the invention are to provide a resistor asdescribed constructed in a fashion for maintaining the leads inpositions sufficiently spaced apart as to prevent dielectric breakdownof insulation disposed between the leads.

In the drawings:

Figure 1 is a cross sectional view taken diametrically through awall-mounted resistor of this invention, a portion of a wall being alsoshown in cross section in Figure 1.

Figure 2 is an exploded view of the wall mounted resistor of thisinvention.

The wall mounted resistor of this invention has an outer housinggenerally indicated at which latter is provided with a larger portion 12adapted to be disposed 2,857,498 Patented Oct. 21, 1958 on one side of awall 14 having an opening 16 therethrough. The resistor 10 has an endportion 20 of smaller diameter than the larger end portion 12, the endportion 20 being of cylindrical shape on its exterior, its exteriorbeing threaded to receive a nut 24 best seen in Figure 1. The nut 24 ispreferably of a heat ond ctive material such as metal and is adapted toengage one side of the wall 14 around the opening 16, the inner end of 1the portion 12 of the resistor overlapping the opening 16 on the otherside of the wall 14 whereby the nut 24 holds the resistor housing 10securely to the wall 14.

The wall 14 shown in Figure 1 represents a section a of a wall forming apart of the chassis of an electronic device of any kind, such wallsbeing ordinarily of metal and being therefore highly heat conductive.For this reason the mounting of the resistor 10 on the wall 14 causes adissipation of heat from the resistor through the wall 14 which hasadvantages in maintaining the housing of the resistor at coolertemperatures whereby the resistor 10 can be made of a more miniaturesize than would be otherwise possible, for the same resistor powerrating.

The larger housing portion 12 is provided with a plurality ofcircumferentially extending spaced apart ribs 30. The larger housingportion 12 and the smaller housing portion 20 of the resistor arepreferably integral and the smaller housing portion 20 has a hollowinterior wall of a cylindrical shape and indicated at 40, thecylindrically shaped wall 40 extending through an open outer end of thesmaller portion 21 of the resistor and inwardly through the housingportion 20 and into the housing portion 12 to a point spaced only ashort distance from the outer end 42 of the housing portion 10,terminating in an end wall 44.

The hollow interior of the resistor is for the purpose of receiving acoil of resistance wire 50 best seen in Figure 2 and wound about theouter side of a resistor core 52 formed of an electrically insulatingmaterial such as ceramic material commonly used in the manufacture ofresistors. The core 52 is preferably of approximately cylindrical shapeon its outer circumference and has a hollow interior, being open at eachend. On the outer end of the resistor core 52 a metal band 56 isprovided extending circumferentially around the core 52 between theouter end of the core and the wire coil 50 which latter is disposedspaced inwardly from the outer end of the core. The band 56 is formed ofan electrically conductive material and the outer end 70 of the coil ofwire 50 is electrically connected to the band 56.

At the inner end of the core 52 the coil of resistance wire 50terminates a short distance from the inner end and a cap 72 is disposedover the inner end of the core 52, the cap 72 having a concave sidereceiving the adjacent end of the core 52. The cap 72 is preferablyformed of electrically conductive material and the adjacent end 74 ofthe resistance wire coil 50 is electrically secured to the cap 72. Afirst lead or terminal of the resistor is disposed adjacent one side ofthe inner wall 40 of the hollow interior of the housing portion 20 asseen in the upper left hand corner of Figure 1. The lead 80 has anopening therethrough at 82 as is common. The lead 36) extends inwardlyparallel to the axis of the resistor housing portions 12 and 20 and isattached by means of a collar to the band 56. The collar 90 ispreferably of cylindrical shape open at its center and is adapted totightly fit around the band 56 for good electrical connection therewithand a portion 94 extends outwardly from the collar 96) and is offsetinwardly therefrom receiving on its outer side the inner end of the lead80 which latter is attached thereto securely for good electricalconnection.

Another or second lead 100 of the wall mounted resistor is disposedadjacent an opposite side of the inner 3 wall 40 of the housing portionZtl. The lead 100 is disposed in parallelism with the lead 80 and withthe wall 40 and has at its outer end an opening 102 similar to theopening 82 transversely through the lead Stl.

The lead ltltl extends inwardly to a point closely spaced from the outerend of the core 52 and has an inwardly inclining transverse portion 103which latter extends inwardly to a point spaced slightly inwardly fromthe inner wall of the hollow core 52 there adjoining an innermost offsetportion 105 of the lead 1%, the portion MP extending inwardly inparallelism with the inner wall of the core 52 and in parallelism withthe axis of the resistor inwardly to a point adjacent the cap 72. Theinner end of the offset portion 1'95 of the lead 1% terminates in aportion 107 set at a right angle to the portion 105 and suitably securedto the adjacent side of the cap 72 for good electrical contacttherewith.

As the resistor is intended to be made on a very miniature size it isvery important that the leads Bill and tilt) are not disposed close toone another at any point. This is the chief reason for the unusualexpedient of placing the lead 100 in the position extending through thecenter of the core 52. To further hold the lead 86 and lltltl apart, aheader 121i) is provided. The header 120 is formed of an electricallyinsulating material, preferably ceramic, and has a cylindrical outersurface for snugly fitting the cylindrical wall 46 of the portion 2% ofthe resistor housing 10. The ceramic header 129 has two parallelopenings therethrough indicated at 122 which are for the purpose ofreceiving the leads fill and Hill. The openings 122 are disposed onopposite sides of the header 120.

At the inner end of the resistor, a plug 13% is provided, the plug 13%)being formed of electrically insulating material and can preferably beformed of ceramic material. The plug 130 is of a cylindrical shapealthough it is thin and has apertures 132 extending therethrough onopposite sides thereof for receiving the leads 8t and 1130. The outercircumference of the plug 130 is similar to the inner circumference ofthe wall 40 for a snug fit.

In assembling the resistor the lead 1% can first be mounted upon the cap72 whereupon the cap 72 is placed upon the core 52 containing the wireresistor coil 59 thereon. The adjacent end 74 of the wire Etl is thenconnected to the cap '72 and the band 56, and the collar 90 is placedthereon, a connection being made between the latter and the adjacent end"ill of the coil 50. The lead 89 can then be attached to the portion 94of the collar 90 following which a Piberglas" sleeve 150 is slipped overthe coil 5a. A suitable insulating material 162 such as silastic, whichis liquid when first applied, is worked into the Fiberglas sleeve 15%filling the pores therein and binding it to the coil 5i Next, a spacerwasher 169 of cylindrical shape and having an open center is placed inthe hollow interior of the resistor housing portion 12 and against theinner end thereof.

The hollow interior of the housing of the resistor is at least partiallyfilled with more of the electrically in sulating material 162,preferably Silastic, which is liquid when it is put on, then later getssolid and has a capacity to withstand heat, retaining its electricallyinsulating qualities after long periods of use.

Next, the resistor coil portion Stl with its sleeve 150 mountedthereover is inserted into the hollow interior of the main or largerportion 12 of the resistor, the space between the sleeve T154 and theinner wall it of the resistor housing being filled with the somewhatliquid insulating material 162 which had been placed in the housing asdescribed before.

in order to insure that all of the interior of the resistor will befilled and leaving no air spaces, the outer end of the resistor housingportion 12 is provided with an opening 170 therethrough which permitsescape of the silastic material 162 as the coil portion 50 of theresistor is inserted into the hollow interior of the housing. Theopening 170 is of cylindrical shape in an outer portion and the opening170 has an inner portion which is outwardly flared as best seen at 172.As thus described, the silastic material 162 is free to flow through theopening 17d and to ooze outwardly of that side of the resistor andbecause the silastic material 162 is capable of flowing and yet isnearly solid, it is very satisfactory for filling the interior of theresistor.

Following this, further silastic is placed in the interior of the coreand sufiiciently to fill a space between the core 52 and the header 12%,this space being relatively thin but of a sufficient thickness forreceiving therein the portion 163 of the lead ltlt) and the portion $4of the collar 9%.

Next, the header 120 is placed over the terminals and liltl and isinserted in the housing portion 2% being then followed by the plug 13%to close the inner open end of the resistor housing. Lastly, theresistor is baked, as is usual.

it will be seen that during use the area on both sides of the Wall 14 isin contact with air in the area substantially around said openingwhereby the wall 14 dissipates heat to the air.

Likewise it will be seen that during use the resistor housing it? is incontact with the air substantially on all outer surfaces thereof exceptadjacent to the wall 14 whereby it cannot dissipate heat in any otherway as easily as it can to the wall 14 because the wall 14 is formed ofmetal which is a material more heat conductive than air.

As thus described, it will be seen that this invention has provided aresistor adapted to be mounted in a wall of a chassis of an electroniccircuit, the resistor being miniature in form in relation to its powerrating and fulfilling the above described objects of the invention.

From the foregoing description, it is thought to be obvious that a wallmounted resistor constructed in accordance with my invention isparticularly well adapted for use, by reason of the convenience andfacility with which it may be assembled and operated, and it will alsobe obvious that my invention is susceptible of some change andmodification without departing from the principles and spirit thereof,and for this reason I do not wish to be understood as limiting myself tothe precise arrangement and formation of the several parts herein shownin carrying out my invention in practice, except as claimed.

I claim:

1. In combination: a resistor having an outer housing having a portionadapted to be disposed through an opening in a wall of a chassis of anelectrical circuit, said housing having a hollow interior open at oneend, a hollow resistor core disposed in said interior, said core beingopen at two opposite ends thereof, a resistor coil disposed around saidresistor core, a cap disposed extending over an inner end of saidresistor core, said cap being electrically connected to the adjacent endof said resistor coil, a first lead attached to the inner side of saidcap and extending through the hollow interior of said resistor core andoutwardly through the other end of said resistor core and outwardlythrough the open end of said housing, a band of electrically conductivematerial disposed around the opposite end of said resistor core fromsaid cap, means connecting the adjacent end of said coil to said band, asecond lead disposed extending through said open end of said housing andinto the hollow interior of said housing, means connecting said secondlead to said band, insulating means filling the interior of said housingin the space between said coil and the interior wall of said hollowhousing, said insulating means being of a type capable of holding itsinsulating properties operably during operation of the resistor.

2. The combination described in claim 1 in which said insulating meanscomprises a material which is before curing a liquid of low viscositywhich is of an electrically non-conductive nature during operation ofthe resistor, said housing having an outlet opening through the endthereof opposite the said open end, said opening being for the purposeof permitting outward oozing of said low viscosity insulating materialwhereby said core can be inserted into said resistor at a time when someof said low viscosity insulating material is disposed in the hollowinterior of said resistor because of the possibility of the oozngoutwardly of said high viscosity insulating material through said outletopening.

3. A resistor as claimed in claim 2 in which a header is provided anddisposed near the open end of said housing, said header being of anelectrically insulating nature and being partially disposed between saidleads and having openings therethrough for receiving said leadstherethrough.

4. The combination claimed in claim 2 in which a filler cap is disposedin the inner open end of said resistor, said filler cap being formed ofelectrically insulating material and having two openings therethroughreceiving said two leads therethrough.

5. The resistor described in claim 2 in which said first lead extendsthrough said core along one side of said core and has an outwardlyextending portion adjacent the opposite end of said core from said cap,said first lead having a portion oflset inwardly from that portionthereof which is disposed in said core, said portion extending outwardlythrough the opening in said resistor having on that side of saidresistor housing which is opposite said second lead.

6. The resistor described in claim 1 in which said first lead has aninner end portion extending through said core closer to the respectiveside of said core than to the other side and said first lead having anoutwardly extending central portion connected to said inner end portionand disposed adjacent the opposite end of said core from said cap, andsaid first lead having an outer end portion ofiset to the side withrespect to said core from that portion thereof which is disposed in saidcore, said outer end portion of said first lead extending outwardlythrough the open end of said resistor housing on that side of saidresistor housing which is opposite said second lead.

References Cited in the file of this patent UNITED STATES PATENTS BurgunOct. 31, 1950

